Newborn calves will have their left lungs denervated, and the mixed pulmonary venous blood from this lung will traverse a plastic conduit prior to joining the blood draining the right lung. This will permit separate measurements acutely or chronically of the blood flow, vascular resistance, and gas (O2 and CO2) exchange of each lung as the result of function of varying cerebral pO2, pCO2, and/or pH. We will study the absolute and relative activity of the pentose phosphate pathway (PPP) in newborn and developing rats as they are exposed to respiratory hypoxia. We will examine the effects of administration of glucose, glucocorticoids, insulin, phenobarbital, and/or phenytoin. BIBLIOGRAPHIC REFERENCE: Hakim, A.M., Moss, G., and Gollomp, S.M., "The Effect of Hypoxia on the Pentose Phosphate Pathway in Brain," J. Neurochem., 26, 683 (1976).